Archaeologists digging beneath Jerusalem's Old City have discovered a huge reservoir near the Temple Mount.

"One day we found an opening in the bedrock," Eli Shukron, an archaeologist with the Israel Antiquities Authority, said. "I put my hand inside to look to see what is going on and we found a huge water cistern."

The cistern dates back to the First Temple built by King Solomon and is one of the largest ever from that time found in Jerusalem.

It's situated close enough to the Temple Mount that experts believe pilgrims used the water for bathing and drinking. It could have also supplied water for everyday activities on the temple itself.

Shukron said the man-made reservoir shows that ancient Jerusalem needed more water than came from a natural spring.

"Not all the water coming from the Gihon Spring, a lot of water coming from water cistern that we found like this here in this area," he explained.

The cistern looks like a cavern dug into solid bedrock. It is about 40 feet long with a width and height of more than 15 feet.

Plastered from top to bottom, it could have held some 66,000 gallons of water.

"The water comes from a tunnel in the Tyropone Valley… and from the valley they move the water into the water cistern," Shukron said.

A small pool of fresh water still exists there today and each new discovery like this helps fill in the picture from thousands of years ago.